Automobile headlight



AUTOMOB ILE HEADLIGHT Fi1ea May 2e, 192e;l 5 Sheng-sheet 2 WA LTER C.PRlC//ARD 30 .the headlight along the main horizontal l the drawingshereto illustrating the inven Patented Feb. 19, 1929. t

UNITED 'STATES PATENT OFFICE.

WALTER. c. rnrcnnnn, orlnnnimnnr,

AU'rorronILE Hnnnnren'r.

- Appnqmon mea may 2e, 192e. 'serial no. 111,696.

This .invention relates to headlights 'for use on automobiles, and hasto doy with a special arrangement of reflecting surfaces and refractingvmeans for determining the shape and dispersion of the projected rays oflight. A

The' objects of the invention' are `to provide improvements in' suchcombinations whereby a more desirable beam isprojected and also whichwill utilize to great advantage more of the emitted rays fromthelightsource'located within the headlight.

As the invention relates specifically to the light controlling surfacesno detail of the headlight body construction is attempted 1n tion.

In the drawings which are half sizel reprepresentation of a full sizedevice, Figure l is a longitudinal central sectional elevation -of,aheadlight embodying the combination of reflecting and refracting meansin'- aocordance with my invention and indicating several .spacedhorizontal.

,reflectors below said axis.

the projection of equally spaced radial rays emanating from its lightsource.

Figure 2 is a similar view showing how some of the rays of the lamp arere-reflected so as to make thein useful in the-projected beam. t 1 eFigure'3 is a horizontal cross section of it is desired to say thatapplicants inventionlies in the specific modification of c'ertain mainreflector forms enclosing the light source, together with thecombination there'- with of other light modifying means, and not broadlyin the general form of the enclosing reflectors from which themodificationsgwere evolved, as thereason for modi- `fication was toproduce a more nearly ideal projectedbeam` thanpossible with the unmo`ified general form, and which being the casefadescription of thereflector forms as by thel action o fthese forms on the light ras.fFeferring to Figure 1 a source of -light is, indicated atv L. and thereflector system\ comprises principally an ovoid upper shel-llextendingdownward to the orizontal axis A,- and a lower ovoid shell 2-enclosing the lowerhalfoffthe 'gure except for an opening at the forwardend of theA combinavmodified'will be entered into, to befollowed i vtionfor the emission of the light rays, and a small hole at the rear end forthe shank 3 A'of the electric globe used as/the light source.

This upper shell 1 is an ellipse of'revolution revolved about one focuscoincident" with the light source and a semi-circle lat v lthe forwardend .indicated by the dotted curve-4 in Figure 5, or in otherI words,revolved about a narrow half cone whose apexv lies at the light sourcepositioned at the rear focus of theellipse.

At the forward end the up er shell is formed with several steps `5, 6,which are portions of spheres traced from the light source or what maybe termedthe principal y.

focus of the headlight.

The lower shell 2 isa compound ovoid whichV before modification was inplan an infinite Vseriesof superimposed ellipses decrea'sing in sizedownwardly, with their lforwardV focl on a common vertlcal locus andwith their rear foci and apices forming parabolas when viewed inelevation, the

'rear apices forming' the rear wall of the lower reflector. Thispfigurewas then bisected vertically and opened up at itforward "end, angularlyfrom the' princitpal focal point L so as to diverge about 8v a ter whichthe halves were tippedl voutwardly about 2' at the bottom only whilefulcrurned on the main focal point L with a result that the originallocus for the forward foci is changed into two loci vertical when viewedin side elevation as'denotedlby the dotted line 8 in Figure l anddiverg'ing slightly downward as indicated by 4the dotted lines 8 and 8in Figure 5 while at viewed in side elevation, land the' side walls aremodified by cleaving them with .an elliptical tube lowered vertically tocut off portions of the side walls and take the place of the portionscuto so as to form vertical wedge shaped walls to a portion of thereliector at opposite sides thereof as indicated at 9 and 9 in. Figure 5merging with the lower reflector along the line 10. The ellipse to whichthis tube is formed is of a size to intersect the original ellipse(dotted Yat 15 in Figure 3) at lextending to the forward end of theheadlight `as per solid outer line while to the rear of point 16 itwould pass outside of the reflector along thel dotted path 17. Therear-focus of theelliptical tube is located at L and the forwardl locusat 18 beyond the loci 8 and 8', the compound reflector being cut olfalong the line 19 spaced back of these point-s.

The upper and lower shells are` suitably held together alon .ahorizontalplane `through the principa focalp'oint'and at the rear end the shank ofthe lamp extends at an upward angle through the reflector while thelreflector gure is further modified to form a paraboloid 11 directly inback of the globe joined to the main reflector walls by an annularspherical portion 12.

Within-the reflecting surfaces is mounted a Ilat rellector diaphragm 13with upper surface horizontal and extending across t0 -op-N posite lsidewalls, while upon the diaphragm 1s mounted a special semi-circular lensor prismatic glass 14 having straight lower walls to the point X andvupwardly c011- verging walls y"above this point.

At the forward end of the reflector system and closing the openin at theline 19 is a glass plate 20 formed with substantially parallel sides atits lower portion and of I varying curved thickness extending straight tacross' the width of the glass at its upper portion on curves struckfrom centers 23 as indicated in Figure 2. This glass is held in positionby a suitably formed outer shell or lamp housing 24 as indicated onFigure 2 which may also be divided along horizontal or vertical axis forassembly, or the lens glass may be supported in any other way desired.

Having thus described the shape and relation of all the reflecting andrefracting ele-` ments it will suiice to show the effect of the`combination on light emitted from L.

lin Figure 1, a series of equally spaced radial lines from L denotingrays (with the exception of the two striking the last forward upper andlower edges of the redector and which are not equally spaced with theothers) show that all rays in the lower shell 2 forward of a verticalline 25 back of the light source are projected horizontally, thosestriking 'the spherical surface 12 are projected back through the lightsource to the 4upper reflector 1, and those striking backward'to theparabolic surface 11 are project-- ed directly forward, any upwarddirection of theserays due to non-theoretical position of light'filament or other direct rays from the lampbeing intercepted by thediaphragm 13, while those immediately abovethe diaphragm in the centralarea pass `through lthe lens 14 and are bent to parallelism asindicated, whilethe rays strikingthe upper re- 'lector are all projecteddownwardly towards ize the central portion of the beam, all as4 clearlyindicated in the ligure by a. simple yin section ofthe rays;

igure 2 omits many of the rays so as to more clearly' show the action ofthe spherical surfaces 5, 6, and 7 in projecting rays, otherwise lost,back through the source of light for' effective reilection from. theparabolic Vsurface 11 `and. from the spherical surface 12 similarly Itothe upper reflector.

Figures 3 and 4 show the eifect of wedging open the lower reflector toform the two loci 8 and 8 at its 'forward end to lessen the angular sidespread.'` of the rays and form a central substantially 8 degree angularcentral beam of almost evenly distributed rays (and practically doublingthe candle power within the angle.)

In Figure 3 the reflection of the ra s along the main horizontal axis isindicate ,and inI Figure 4 the ovaloid lines within the reflectorindicate e ually spaced horizontal planes a, b, c, al, and e below themain axis, while the rays are supposed to be lvertical* planes of lightso as to ,show their reflection from points of impingement at thesehorizontal planes. t

All rays below the main horizontal axis striking the vertical walls 9and 9 are retlected downwardly as well as forwardly, thus causing therearmost projected rays 26 and 26 to strike the ground about 41/2 feetin front of the car and aboutl'thesame distance outside of the oppositewheel.

'llhe angular tippingl of the sides to diverge the loci 8 and 8downwardly results in tipping the otherwise horizontal transverse planesof forwardly projected horizontal rays' two degrees downward toward thesides of the road so that the upper surj ecting face of the projectedbeam from the headlight presents a slight gable roof formation, i thuskeeping the surface of the beam within, a general horizontal plane whereit meets an oncoming motoristeven tho the vehicle arch of the road, y y

The small semi-circular 'lens 14 is best secured to thediaphragm bycementing or with a very thin metal strap 37 as indicated in Figure 6and the function of this lens is to intercept the direct rays from thelight carrying my headlight is to one side of the :source'which wouldotherwise leave the head.-

light at an upward angle, andv bendgthem downwardinto the mainv beam atandV below the horizontal, so as to avoid any such upwardly slantingrays lcausing a glare to an approaching motorist.

The compound curvature ofthe upper porv-v tion of the forward glass 20is such as'to intercept the sharply descending rays from the upper frontportion of the upper reflector which ordinarily would strike the groundtoo near the car, and bend them -for projection further along the roadfor strengthening the light field in the middle distanceA while at thesame time it bends downward the near horizontal ra sjfrom the forwardportion of thesides o the upper reflector so asto better illuminate thesides. of4 the road.

The peculiar formation of the upper reflector through revolving anellipse around' a hemi-cone as described results in its pro-l a moreeven and concentrated beam of lig t than produced by a hemi-ellipsoidgiving a similar effect as the' spreadingof the forward locus of thearent lower reflectorffrom the center to t e loci 8 and 8', infactvforming a curvedlocus for the upperk reflector joining vsaid loci. 4 i

If it'were possible to lobtain a point light source at the focalpoint ofa hemi-ellipsoid reflector without any supporting member to interceptany ofthe rays, the beam or light field projected would bea half-conewhich 'wouldproduce a semi-circle light field on v`a screen a shortdistance in front of the re-j flector, the light. -being most intense atthe center and tapering off toward the outside. With the best presentavailable light source, the incandescent electric light, inserted thruthe apex ofthe ellipsoid the portion ofthe reflector which shouldproject the lrays to the center ofthe field would be missing and`Certain rays from the portion of thereflector behind the lamp beingrefracted and reflected by the glass of the lamp cause a. dark spot orshadow in the center of the field where 'the light should be brightest.

The above reflector not only does away.

with -this dark spot but actually overlaps the rays from the two sidesforming av spot of'high intensity at the Acenter where it is needed themost.

described, a reflector ta in The vertical walls 9 and 9 vthrough theireffect in reflecting the rays downwardly and throught-he locus 18 areparticularly effective inwlighting the side of the road and the ditch.

I claim:. 1.v Inj a"'l1e a`dlight of the character described, an`ovoidal reflector the portion above the main horizontal axis of' whichtakes the form of a heini-ellipse of revolution revolved around thecurved wall of a heini-cone whose apex lies at the light source and oneof the foci of the ellipse; and the portion below said horizontal axistakes a form derived from a bod elliptical in horizontal crossl sectionsan arabolic on vertical sections, said body eing split vertically onitscenter line and angularly spread at its forward end while fulcrumed atthe light'source. `2. In a headlight of the character del scribed, anovoidal reflector the portion above the main horizontal axis of whichtakes the form of a hemi-ellipse of revol'ution revolved around thecurved wall of ahemi-cone whose apex lies at the light source and oneofthe foci of the ellipse; and the portion below said horizontal axistakes a form derived froma bod'4 elliptical in horizontal cross sectionsan arabolic on vertical sections, said body eing split vertiarea'flaring forwardl In a vehicle hea described, a reflector ta 'nv ltheform substantially as specified in c aim 2- and cut off vertically atits forward end within its li ht of the character I outer focus, a light.source'at the other focus,l 1 a glass plate closing the cut o'ff end ofthe figure `provided with substantially parallel l Walls at its lowermajor portion and withl ray modifying curvatures at its upper portiononly adapted to` bend upwardly some of the upper rays above-the main'horizontal axis of the headlight onl 4. In avehicle4 headli 1t of thecharacter stantially as specifiedl 'n' cllaim 2 and cut off verticallyat its. forward end within its outerfocus, a light source at the otherfocus,

figure provided with substantially parallel walls at its lower majorportion and with ray modifying curvatures at its upper por-- 5. In avehicle headlight of the character .a glassplate closing the cut/off,end of the t izo forward end within its outer focus, a, light' 5positioned lat its inner main focus, and the sides of sald ovold belowlts main horlzontal axis only including forwardly Haring segments ofsubstantially vertical Walls following in plan the outline of an ellipseWhose inner focus is substantially coincident with said light and itsouter focus beyond the outer focus of the ovoidal body.

WALTER C. PRICHARD.

